An image decoloring apparatus which decolors an image formed on a sheet by an image forming apparatus such as a MFP (Multi-function Peripheral) and the like has been used. The image serving as a decoloring target is formed using a coloring agent having decoloring characteristic such as ink containing leuco dye and the like.
The coloring agent having decoloring characteristic has a property that decolors the color thereof by applying a high temperature thereto. Thus, the image decoloring apparatus can heat the sheet to decolor the image formed on the sheet. An example of such an image decoloring apparatus is disclosed in Japanese Unexamined Patent Application Publication No. Hei 10-161492, U.S. Pat. No. RE37197 and the like.
When conveying a sheet nipped by a heat roller and a press roller, the image decoloring apparatus heats the sheet to decolor the color of the coloring agent. Decoloring sections each of which consists of a heat roller and a press roller are arranged at the upstream side and the downstream side of a conveyance path of the sheet, and are constituted in such a manner that images on the two surfaces of the sheet can be decolored.
The sheet conveyed by the image decoloring apparatus is heated by a decoloring section at the upstream side and then conveyed to a decoloring section at the downstream side. As a result, compared with the decoloring section at the upstream side, it is not required for the decoloring section at the downstream side to apply that much heat to the sheet. Thus, in a case in which the heat rollers that are respectively arranged at the upstream side and the downstream side have the same heat capacity, the decoloring section at the downstream side is provided with an unnecessarily large-sized constitution, which leads to increase in power consumption.